Mill for rolling metal



Feb. 2, 1932. L. JONES MILL FOR ROLLING METAL Filed Jan. 18, 1928 Patented Feb; 2, 1932 LLOYD JONES, or SALEM, omo

1mm FOR ROLLING METAL Application filed January 18", 1928. Serial No. 247,612.

This invention relates to mills for rolling metal and more especially to a rolling mill in which provision is made for maintaining an even or uniform gauge in the material delivered by the rolls from end to end of a given piece of material, or from beginning to end of a series of pieces.

In the rolling of material, particularly of strip or sheet materials, it is of great importance that the strips or sheets be of uniform gauge from one side to the other and from end to end. If the material delivered tothe mill is of substantially evengauge from end to end, and the rolls of the mill are properly shaped to give the minimum degree of variation from edge to edge that can be maintained in commercial rolling practice, then the remaining causes of gauge variation will be found to result from variations in the hardness of the material being rolled, or from variations in the dimensions or shapes of the rolls of the mill due to changes inthe temperatures of the rolls. The present invention relates to the preventation of variations in gauge, due to changes in the dimensions of the rolls of the mill, and particularly such variations as are produced by the heating of the rolls.

According to the prior art, it is the usual practice to provide rolls of fairly large diameter which run slowly so that they may bemaintained at a normal temperature, due to natural air cooling, which compensates for the heat that they absorb during the operation" of rolling. It is also a common practice to direct blasts of hot 'or cold air, or streams of water or other fluids, against the surfaces of the rolls to control the temperatures thereof and to maintain these temperatures as nearly as possible to what is considered normal working temperatures. During the intervals between rolling, the rolls are sometimes heated by gas or electric heaters. All of these methods require considerable skill and attention on the part of the rolling mill operative, and they are not satisfactory when used in connection with small high speed rolls.

The present invention difiers from the prior art in that it contemplates a form of mill or rolls for a mill in which, within the temperatures produced in the mills by rolling material therein, and irrespective of any means for controlling the temperatures of the rolls, the gauge of the material passing through the mill may be kept substantially constant.

In a more specific aspect, the invention contemplates a mill roll in which the amount of expansion of the 'roll is very low as compared to rolls heretofore used, so that within the temperatures experienced in rolling material the changes in diameter in the roll due to heating are so small as to be practically negligible in their effect on the gauge of the material being rolled.

Another ob'ect of the invention is to pro-' vide a roll for a mill having a hard outer surface and an inner body expandable only to a very slight and negligible degree by the rolling heat so as to reduce materlally the gauge variations.

To these and other ends, the invention consists in the novel features and combination of parts to be hereinafter described and claimed. r

The single figure of the drawing shows somewhat diagrammatically a rolling mill having my invention embodied therein.

For convenience I shall now describe m invention in connection with the two roll shown in the drawing, but it is to be understood that the features of the invention are adapted for application to any of the well known types of mills, and are-notably useful in connection with the metal engaging rolls of four high mills, cluster mills, etc.

' The mill shown in the drawing comprises in general a frame. 2 having mounted therein in suitable bearings a lower roll 3 and an upper roll 4, the lower roll 3 usually being mounted in relatively fixed bearings, while the upper roll 4 is mounted in -adjustable bearings and is held against movement away from roll 3-by suitable means, as for example,-

screw 5, mounted in head 6 of mill frame 2 and adjusted by hand wheel 7. The material 8 having an initial thickness T enters rolls 3 and 4 at A, and passes from between the rolls with a final thickness of T The rolls at the beginning of the operation of rolling may have the temperature of the room in which the mill is located, and the increase in temperature in the rolls may partly be due to the fact that the material'being acted on enters the mill at a higher temperature than 'the room temperature, resulting from the fact that the material may have been heated by being previously acted on by another mill, or

by the annealing processes which usually occur between rolling operations. To this is added the heat due to overcoming the internal molecular friction during the act of rolling, and heat due to the surface friction between the rolls and material at all points in the passage of the material between the rolls where the surfaces of the material and rolls move at different speeds. It will be readily understood that the eflect of the heat added to the rolls is such as to cause the rolls to increase in diameter, thus decreasing the amount of clearance between the rolls, and

causing a reduction in the gauge of the material passing therebetween.

When the roll surfaces are large and the speed of rotation slow, the usual methods of controlling the roll temperatures are to a certain extent effective, but when it is desired to increase the roll speeds, or to more closely control variations in diameter to give less gauge variation, then the usual temperature controlling methods become unsatisfactory.

In the present invention, the control of the roll dimensions, and therefore gauge variations, is effected by providing rolls substantially non-expandable by the rolling heat. These rolls are made of material having a low coefficient of expansion as compared to iron or steel, or the ordinary alloys ordinarily used in roll manufacture A material having less than one-half of the coeflicient of expansion of ordinary iron or steel, that is, a coefficient of linear expansion of less than 0.000003 per degree Fahrenheit, will be found to give excellent results, and to this end it is proposed to use, for example, an alloy composed of iron and 33 to 38% nickel. Such an alloy has a coeificient of linear expansion of approximately 0.0000002 per degree Fahrenheit, and where the hardness of the alloy is sufficient, rolls made therefrom will give remarkable results in controlling variations in the gauge of the material passing through the mill. Regardless of the particular material used, a roll of myinvention, whether it be a metal-engaging roll or a backing-up roll, will increase in diameter less than .0003 of one percent for each increase of average temperature of one degree F. in the roll. In certain cases, it may be desirable to have a harder roll surface than ordinarily possessed by the alloy described above, and while this may be brought about in a number of ways it is preferred to provide a core formed of the alloy and a thin aeeaevo outer shell of harder material, such as steel or a suitable alloy such as stellite, tungsten steel, etc., which may be attached to the core by being shrunk, amalgamated, welded, cast or plated thereon, or attached in any other manner that may be suitable according to the character of the outer shell. A roll formed in this manner will present a hard outer surface capable of rolling the harder metals, and yet will possess the low coeflicient of expansion desirable in preventing changes in the gauge of the metal being rolled. It is desirable in rolls of this type to have the outer shell as thin as possible so as to reduce the expansibility of the roll as a whole as much as consistent with its surface hardness and durability. The outer shell should be secure ly locked or held to the core;-for example, by being made in one piece therewith by welding, or the like, so that the shell, which is limited in its expansion by its thinness, is firmly held to the comparatively large substantially non-expanding body constituting the greater part of the roll. Such a roll will be substantially non-expandable by the rolling heats which obtain in ordinary cold or hot rolling of metal within the ordinary limits in practice. Such a roll will be substantially unexpanded by a rise in temperature not exceeding 400 F. V

In the mill shown in the drawing I have providedan upper roll made throughout of a material having a low coefficient of expansion while in the lower roll 3 there is provided a hard relatively thin outer shell 9, with an inner core 10 of material having a low coeficient of exp'ansion. It will be readily understood, however, that if desired both rolls can be made with hard outer shells, or both rolls can be made of the same material throughout.

When rolls such as those disclosed above are used in rolling mills in connection with the ordinary means for controlling temperatures, such as blasts of air or streams of water, etc., much less care and skill on the part of the operative is required, and in many instances the ordinary'means for controlling the temperatures may be dispensed with altogether.

While I have shown and described a preferred form of my invention, it will be understood' that it is not to be limited to all the details shown and described but is capable of modification and variation within the spirit of the invention and within the scope of the appended claims.

What I claim is: p

1. In a mill for rolling metal, a metal engaging roll for reducing the metal. inherently substantially non-expandable by an increase of temperature of 400 F.

2. In a mill for rolling metal, a pair of rolls forming a pass for reducing the metal and inherently substantially non-expandable by an increase oftemperature of 400 F.

3. A metal reducing roll having a relatively hard outer surface and an inner core having a coefficient of expansion of less than .000003 per degree F.

4. A rolling mill roll having a relatively hard outer surface and an inner core of an alloy of iron and nickel, the nickel content of the alloy being from 33 to 38%.

5. A rolling mill roll which per se is substantially non-expandable by an increase of temperature of 400 F.

6. A rolling mill roll whose diameter will increase less than .0003 of one percent for each increase of average temperature of one de ree F. in the roll.

A rolling mill roll whose diameter will increase less than .00015 of one percent for eachincrease of average temperature of one degree F. in the roll.

8. A rolling mill roll whose diameter will increase less than .0003 of one percent for each increase of average temperature of one degree F. in the roll, said roll being relatively harder at its outer surface than inwardly thereof.

9. A rolling mill roll whose expansibility under heat is substantially less than half of that of a cast iron roll of the same dimensions.

10. A rolling mill roll whose expansibility under heat is substantially less than half of that of a cast iron roll of the same dimensions, the workin surface of said roll being substantially har er than ordinary cast iron.

11. A rolling mill roll having a hard outer surface and provided with an inner body such that the roll diameter will increase less than age temperature of one degree F. in the roll. 12. A rolling mill roll for preventing gauge varlations in rolling due to roll expansion under heat and comprising a large inner body of a material having a coefiicient of expansi%r1 materially less than .000003 per de gree 13. A rolling mill roll including in its structure a body of metal substantially nonexpandable by an increase of temperature of 400 F.

14. A rolling mill roll for limiting gauge variation in rolling, including in its struc- 5 ture a large inner body vof a ferrous alloy having a co-eflicient of linear expansion not more than one-sixth that of ordinary cast 1ron.

15. A rolling mill roll whose expansion under the efiects of rolling heat is practical ly nil, the periphery of the roll being of a difi'e'rent constituency from the inner body and substantially harder.

16. A metal-engaging rolling mill roll at .0003 of one percent for each increase of averposed of metal substantially non-expandable y ordina rolling heats.

17. Ar dllling mill roll for limiting gauge variation in rolling, having an inner body whose coeflicient of expansion is less than .0000015 per degree F. g

18. A pair of cooperating metal reducing rolls whose bite is inherently constant in dimensions regardless of variations of temperature within 400 F. to which said rolls are subjected.

19. A pair of cooperating metal reducing rolls whose bite under changes of rolling temperature within 400 F is inherently limited in dimension" so as to roll a sheet of substantially uniform thickness from end to end re ardless of such chan es.

n witness whereof, have hereunto set my hand this 9th day of January, 1928.

LLOYD JONES. 

